Three models are proposed of how words might be stored in the mental lexicon. The Whole Word Model claims that morphologically complex words are listed in an unanalyzed form, just like simple words. The Stem Model claims that complex words are stored as stems, with prefixes listed as subentries. Finally, the Stressed Syllable Model claims that all words, both simple and complex, are stored by their stressed syllable. Three experiments are proposed to distinguish empirically among the models. In each experiment, subjects are asked to make a lexical decision about strings of letters exhibiting various patterns of stress and morphology. The three models make differential predictions about which strings should be most easily recognized.